<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>登录</title>
    <style>body{font-family:Arial,sans-serif;margin:0;padding:20px;display:flex;justify-content:center;align-items:center;min-height:100vh;background:#f5f5f5}.login-box{background:white;padding:20px;border-radius:5px;box-shadow:0 2px 10px rgba(0,0,0,0.1);width:300px}h2{margin-top:0;margin-bottom:20px;text-align:center}.input-group{margin-bottom:15px}input{width:100%;padding:10px;border:1px solid #ddd;border-radius:4px;box-sizing:border-box}button{width:100%;padding:10px;background:#007bff;color:white;border:none;border-radius:4px;cursor:pointer}</style>
</head>
<body>
    <div class="login-box">
        <h2>用户登录</h2>
        <form onsubmit="alert('登录成功!');return false">
            <div class="input-group"><input type="text" placeholder="用户名" required></div>
            <div class="input-group"><input type="password" placeholder="密码" required></div>
            <button type="submit">登录</button>
        </form>
    </div>
</body>
</html>